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5 axis programming

dcrace

Aluminum
Joined
Jun 26, 2002
Location
U.S.A.
Hoping someone can shed some light on my brain-melting confusion of 5 axis programming...

Machine is a Mazak VC-500. B axis table rotates about Y and C is Z.

We run these parts in another 5 axis (Doosan, A is along X axis) using G68.2 coordinate rotation. I did not write the original program, so I am still trying to understand how the G68.2 is defined.. Due to some tight true position tolerance, we also probe each part when loaded on the fixture for X/Y pos. and rotational error in the C axis. Part is programmed from the common origin regardless of rotary position.

Original code:

A-90.C90.
G68.2X0Y0Z0I90.J-90.K0 (A pos. is 90, why I90.?, C is 90 / why J-90. and not K90.?)

G53.1
X0Y-.7
G43Z1.6265H06M8

When we bought the machine, we were told to program using G54.2 dynamic work offset and also sold the G54.4 WSEC option ($900.00) and we wouldn't need to use G68.2?

The apps guy took our original Doosan program and modified it calling up G54.2 after positioning the rotary:

G90G54G00G69
B-90.C90.
G54.2 P1 X0.7000 Y-0.0000 Z10.
Z1.6265 M08

Once he came in and assisted in getting this running, he changed the program to use a DIFFERENT style of G68.2 programming because he said it had to be that way because we probe the parts??G0B-90.C90.
S2838M03

B-90.C90.
G68.2 P3 Q1 X0 Y0 Z0 I0. J0. K1.
G68.2 P3 Q2 I0. J-1. K0
G53.1
X0.7000 Y-0.0000 Z10.

Z1.6265 M08

Once again, confusing me as the explanations I have found are confusing.

Fusion outputs the G68.2 different also:

G0 B-90. C90.
G68.2 X0. Y0. Z0. I0. J90. K90. (shouldn't "J90" be "J-90."?)
G53.1 P1

if anyone can explain, it would be appreciated as I haven't yet found a complete description of the tilted workplane or if the part can be programmed using G54.2/G54.4 using the probing cycles. I have also seen talk about a macro to probe the part, calculate the difference from COR and populate the G54.2 or G54.4 but haven't seen a complete or proven example for the Mazak.



Thanks in advance.

If the simple way is to position the rotary, Call up G54.2 and program off the origin of the part, then sign me up
 
I read your whole post, and the only question I can construct is how to change J90 to J-90.

Or you actually need it to rotate 90° in the opposite direction.

I don't see anything else.

R
 
G68.2 is a tough nut to crack. The Fanuc 5 axis manual has a very informative chapter explaining it's use. You will need to read it a couple of times to wrap your head around what is going on. That's not the fault of Fanuc but the mechanics of Eulers Angles. It's better understood on an A Axis machine because that's how the rotations take place with Eulers Angles. Your output will not be the same between an A Axis machine and a B Axis machine. On a B Axis machine, there will be an additional rotation, the K value in your case. There is absolutely nothing wrong with using G68.2. In fact, there is a distinct advantage because G68.2 will use the built in kinematics parameters just like G43.4 (TCP) does in full 5 axis machining. But that means you will have to maintain those kinematics parameter. On your Doosan, you should have DCPi in your EOP screens.

Also, Fanuc provides 5 different types of G68.2, 2 of which are most common. Eulers Angles and simple roll, pitch and yaw. Default is Eulers.

Paul

Edit: I work for Doosan. What Doosan machine do you have? Email me at the below address and I can send you what I have on G68.2.

Paul Anderson
Applications Engineer
Doosan Machine Tools
[email protected]
 
Last edited:
Hey dcrace, I work out of the Mazak northeast office. Feel free to give us a call to discuss your problem in more detail, you can PM me here too.

You will be fine using G68.2 for what you need to do. It is all I use for 3+2 work, the machine will do all calculations for part movement automatically. If you're where I think you are, I'm pretty sure I know what's going on.

Mazaks default to the Eulerian angles method for G68.2. This would be G68.2 P0 techincally. Here are all the setting methods:

Eulerian angles - G68.2 (P0)
Roll, pitch, yaw - G68.2 P1
3 points in plane - G68.2 P2
2 Vector - G68.2 P3 (the one you seem to be currently running)
Projection Angles - G68.2 P4
Tool axis direction G68.3

I generally use eulerian or roll, pitch, yaw; that's also how most CAM software are setup. What you need to do is figure out what method your Doosan defaults to and what method fusion is outputting. From the looks of it, I'm guessing eulerian as well, but it can be confusing.

Probing with Renishaw inspection plus is supported under G68.2, but there is an extra step involved. You need to call "G43 P0" to reactivate the probe length once under G68.2. Here is an example:

G49
G69
G0 G53 Z0. (HOME Z)
G54.1 P5
G68.2 P1 X0. Y0. Z0. I0. J-90. K0. (ROTATE COORDINATE SYSTEM) (B-90., C0.)
G53.1 P1 (ACTIVATE NEW ROTARY POSITION)
G43 P0 X0. Y0. Z5.0 H#3020 (RE-ACTIVATE PROBE TOOL LENGTH)
G65 P9810 Z1.0 F200. (START POINT)
G65 P9814 D0.5 Z-.25 (MEASURE FIRST POINT)
G65 P9811 Z0. (MEASURE POINT IN Z)
G65 P9810 Z6.0 (Z CLEARANCE)
M1

You also need parameter F144 bit 1 = 1 and SU158 bit 3 = 1

I wouldn't bother with G54.2 or G54.4 for your machine, there aren't many advantages to them for that style machine. That was just the old way of doing it with dynamic offsts. Like I said, G68.2 does all the stuff internal to the function as a nature of how it works. Let the machine do the work is my motto.
 
G68.2 is a tough nut to crack. The Fanuc 5 axis manual has a very informative chapter explaining it's use. You will need to read it a couple of times to wrap your head around what is going on. That's not the fault of Fanuc but the mechanics of Eulers Angles. It's better understood on an A Axis machine because that's how the rotations take place with Eulers Angles. Your output will not be the same between an A Axis machine and a B Axis machine. On a B Axis machine, there will be an additional rotation, the K value in your case. There is absolutely nothing wrong with using G68.2. In fact, there is a distinct advantage because G68.2 will use the built in kinematics parameters just like G43.4 (TCP) does in full 5 axis machining. But that means you will have to maintain those kinematics parameter. On your Doosan, you should have DCPi in your EOP screens.

Also, Fanuc provides 5 different types of G68.2, 2 of which are most common. Eulers Angles and simple roll, pitch and yaw. Default is Eulers.

Paul

Edit: I work for Doosan. What Doosan machine do you have? Email me at the below address and I can send you what I have on G68.2.

Paul Anderson
Applications Engineer
Doosan Machine Tools
[email protected]

You caught something I overlooked, that the Doosan has an A and the Mazak has a B. That will change the I, J, K values; at least for roll, pitch, yaw method.
 








 
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